K – 2nd grades
Difficulty of Project
Less than $5.00
To prevent drowning, young children should not be left unattended around water
Readily available or easily purchased at a grocery store
Approximate Time Required to Complete the Project
Less than 30 minutes to collect the data; one day to prepare the science fair display.
To investigate the density of salt water
- Large, clear jar
- Measuring spoons
Prior to starting this investigation, review the concepts of sink and float. Two factors affect an object’s ability to sink or float: density and buoyancy. An object sinks because it is denser or heavier than the water. Adding salt to the water causes the water to become denser.
In this investigation, the egg floats in the salt water because the salt water is denser than the egg.
density: how heavy something is for its size
buoyancy: the force that causes something to float
Salt water is denser than fresh water. Because of its density, things float more easily in salt water.
- Why do some things float and some things sink?
- Is it possible to make an egg float?
- Gather the necessary materials.
- Fill the jar with about ¾ full with water.
- Carefully place the egg in the water. Observe and record results.
- Remove the egg from the water.Add one tablespoon of salt to the jar of water.
- Carefully place the egg in the water.Observe and record the results.
- Continue to repeat steps 4 and 5 each time adding an additional tablespoon of salt until there is a noticeable change.Observe and record the results after each addition of salt.
“Density and Buoyancy: Making Eggs Float” at www.teachersdomain.org/resource/phy03.sci.phys.matter.zegg/
“Principle of Buoyancy” at www.bookrags.com/research/buoyancy-principle-of-wop/
“Buoyancy Basics” at pbs.org
“Float, Sink or Swim” by Anne Hance at www.explorit.org, 1994